Scripting Bridge for iTunes

Question

I'm trying to do something simple and efficient with scripting bridge and iTunes, which is to display the number of the track currently playing in the playlist (aka "get index of current track"), so here's my try:
// initialization
iTunes = \[ SBApplication applicationWithBundleIdentifier:@"com.apple.iTunes" \] ;
// repeat this on a timer
iTunesTrack* currentTrack = \[ iTunes currentTrack \] ;
iTunesPlaylist* currentPlaylist = \[ iTunes currentPlaylist \] ;
SBElementArray* currentTracks = \[ currentPlaylist tracks \] ;
NSInteger index = \[ currentTracks indexOfObject: currentTrack \] ;
but this doesn't work because currentTracks and currentTrack are references that haven't been evaluated (and indexOf doesn't persuade them to evaluate). This can be fixed by:
NSInteger index = \[ \[ currentTracks get \] indexOfObject: \[ currentTrack get \] \] ; // leaks mem!
and while the index is now correct, this leaks memory (about 1K bytes per call - alot more after some time!). Am I doing something wrong? Does Scripting Bridge have a memory leak? Is there a better way to get this index, or am I stuck going back to AppleScript (I promised myself I'd quit if it got messy). Thx, -L.

Answer 1

Thanks again for your collective guidance - per your advice, I've tried allocating and releasing an autorelease pool every get/loop. In fact, I've tried many variations of draining and releasing pools, as well as variable assignments and releases. No change in the memory leak.
I'm starting to suspect that the leak is lower-level than anything Objective-C is doing, but please correct me!
I've distilled the problem into just a few lines of code inserted into the generic Cocoa app template generated by Xcode. Please take a look below and see how one might change it to not leak memory - Activity Monitor says it ticks up .01MB (about 10K) in RSS memory usage every few seconds.
Thanks for your continued guidance, -Lance.
// generated a skeletal Cocoa app (just removed generic copyright comments, added startTrackWatcher)
// generate iTunes.h with sdef /Applications/iTunes.app | sdp -fh --basename iTunes
// and add ScriptingBridge framework to project
#import <Cocoa/Cocoa.h>
int main(int argc, char *argv[])
void startTrackWatcher() ; // added these two lines
startTrackWatcher() ; // for watching mem leak
return NSApplicationMain(argc, (const char **) argv);
// added lines below for startTrackWatcher
#import <ScriptingBridge/ScriptingBridge.h>
#import "iTunes.h"
@interface Status : NSObject {
@public
NSTimer* timer ;
iTunesApplication* iTunes ;
- (void)doit:(NSTimer*)timer;
- (Status*)initWithTime:(int)time;
@end
@implementation Status
- (void)doit:(NSTimer*)t
// NSAutoreleasePool* pool = [[ NSAutoreleasePool alloc ] init ] ;
iTunesTrack* currentTrack = [ iTunes currentTrack ] ;
iTunesPlaylist* currentPlaylist = [ iTunes currentPlaylist ] ;
SBElementArray* currentTracks = [ currentPlaylist tracks ] ;
// NSInteger index = [ currentTracks indexOfObject: currentTrack ] ; // wrong because items aren't evaluated
NSInteger index = [ [ currentTracks get ] indexOfObject: [ currentTrack get ] ] ; // leaks memory (check Activity monitor)!
printf( "%d
", index ) ;
// [ pool drain ] ;
// [ pool release ] ;
- (Status*)initWithTime:(int)time {
/NSAutoreleasePool pool =*/ [[NSAutoreleasePool alloc] init];
timer = [NSTimer scheduledTimerWithTimeInterval:time
target:self
selector:@selector(doit:)
userInfo:timer
repeats:YES] ;
iTunes = [ SBApplication applicationWithBundleIdentifier:@"com.apple.iTunes" ] ;
return self ;
@end
void startTrackWatcher() {
[[ Status alloc ] initWithTime:0.1 ] ;